1. Field of the Invention
This invention relates to a method of and an apparatus for applying top end stops to a slide fastener chain of continuous length. More particularly, the invention is directed to such a method and apparatus which is employed during a substantially continuous cycle of operation in which the slide fastener chain is attached with bottom end stops, threaded with sliders, attached with top end stops and finally cut to individual product lengths.
2. Prior Art
The present inventor has previously proposed a technology of applying top end stops to a slide fastener chain as disclosed in U.S. Pat. No. 4,839,956, in which a pair of opposed stringer tapes are spread apart under tension along their respective inner longitudinal edges and inserted, upon release of the spreading tension, through the respective U-shaped top end stops of a plastics material which are received in correspondingly shaped pockets defined between a clamping jaw and an anvil, and the top end stops are secured to the stringer tapes by means of ultrasonic or high-frequency energy after the clamping jaw has been retracted away from the anvil. This prior technology however involves a mono-functional apparatus which is not suitable, if not impossible, for employment in the aforesaid continuous cycle of slide fastener finishing operation. It would be possible to thread a pair of stringer tapes at their leading ends through the U-shaped top end stops which are clamped between the jaw and the anvil, but the tendency is that the threading force or sliding resistance of the stringer tapes causes the end stops to become shifted out of the correct position on the anvil particularly when the jaw is separated from the clamping jaw, resulting in defective or inoperative top end stops on the stringer tapes.